After updating Vista to SP1, the clock in the sidebar seems to have changed: the minute hand now only has 60 possible positions (i.e. it points exactly to the minute marks), whereas before, it seemed continually variable (e.g. at 22:59:55, the minute hand would be nearly vertical, rather than pointing to the "59" mark.)
I wonder why they changed that. The behaviour had confused me briefly at first, but I had got used to it—now I have to get un-used again! And it doesn't match what many analog clocks do, either. And why should that sort of behaviour come in a service pack? It's not like it's a security vulnerability, and I'd be surprised if it's a performance enhancement.